The Big and Little Dipper

 This time of year the two asterisms known as the Big Dipper and Little Dipper stand high in the northern sky.  These two star patterns are part of the formal constellations Ursa Major and Ursa Minor.

Sony A7iii + Laowa 15mm f/2 + Softon filter.  ISO 1600, 30 s.

Little Dipper.  Hoya Softon filter.

Sony A7iii + Laowa 15mm f/2 + Sparkle-6x filter.  ISO 1600, 30 s.

Little Dipper.  Hoya Sparkle-6x filter.

I like both of these two filters.  The Softon filter gives the stars a more natural appearance.  The Sparkle-6 filter results in a more artistic flair.

For those not familiar with these star patterns, here is a finder chart:

credit: SkySafariAstronomy.com

The sky brightness when these images were obtained was sqml=21.69 mpsas.  See the previous post for an explanation of this number.

Zodiacal light over Bristol Head

 The dark skies of Creede are a welcome change from the urban murkiness of Santa Fe.  Last night the measured sky brightness here was sqml=21.69*, which is very dark indeed. There were some clouds still skating across the sky, but a brief opening provided a view of the Zodiacal light over Bristol Head.  The Zodiacal Light is a diffuse glow caused by sunlight scattering from dust particles in Earth's orbital plane.  Most of the dust is believed to originate from Mars.

Sony A7iii + Sony FE 20mm f/1.8 G + softon filter.  ISO 1600, 30 s

The yellow line in the chart below represents the Ecliptic, Earth's orbital plane.

credit: SkySafariAstronomy.com

The following night, an hour earlier:

Sony A7iii + 20mm f/1.8 G + sparkle-6 filter.  ISO1600, 30 s.

Big Dipper

 *Sky brightness is measured in units of magnitude per square arcsec (mag/arsec²) or MPSAS.  A device called the Sky Quality Meter-L (sqml) manufactured by the company Unihedron is used to measure this quantity.   

More double stars, with the Celestron C6

 The previous double-star results with the Sky-Watcher Skymax 102 MCT were sufficiently pleasing that I decided to try some more-challenging targets with a larger telescope, the Celestron C6 SCT (Schmidt-Cassegrain Telescope).  The nominal focal length (1500 mm) of this scope was increased to 3750 mm with a Tele Vue 2.5x Powermate.  Combined with the 0.0033-mm pixel size of the E-M5iii camera this yields an image scale of 0.18 arcsec/pixel.

Here is a list of the double stars and their nominal separations in arcseconds:

• Izar (Epsilon Boötis) : 2.9"
• Mizar (Zeta Ursae Majoris) : 14.4"
• Pi Boötis : 5.5"
• Xi Boötis : 4.8"
• Rigel (Beta Orionis) : 9.5"
• Porrima (Gamma Virginis) : 3.4"

Izar is the closest pair in this set and was initially difficult visually, until I realized that the collimation of the scope needed to be tweaked.  After a fairly small adjustment it became easy to separate with the bluish secondary appearing as a tiny pinprick next to the yellowish primary.  It is hard to capture that view with the camera because atmospheric turbulence blurs the image.  Most of these images were taken with a shutter speed of 1/4–1/2 s at ISO 1600 and are stacks of 2–4 of the sharpest separate exposures.

Here is a finder chart showing the location of the three double stars in the constellation Boötes:

credit: SkySafariAstronomy.com

Celestron C6

As usual, click on an image to get to the larger version.

The Christmas Comet of 2018

 Comet 46P/Wirtanen is a periodic comet discovered in 1948.  It orbits the sun with a period of 5.4 years with a distance varying  between 1.05 AU and 5.17 AU (1 AU = radius of Earth's orbit).  In 2018 it made an unusually close approach to Earth (about 7 million miles) on 16 December and achieved naked-eye visibility (magnitude 4).  It was the brightest comet of 2018 and was dubbed the "Christmas Comet" by some news sites.  

During the close approach it was possible to detect  the comet's motion over a period of less than ten minutes.  I did not record the lens I used for these photographs.

Comet 46P/Wirtanen near the Pleiades, 16 Dec 2018.  E-M5, ISO 800, 15 s.

8-min interval.  Comet is moving right to left.

Through the clouds. 15 December 2018.

15 December 2018

14 December 2018

13 December 2018

11 December 2018

Some of these images are corrected for purple-fringing (a common flaw with old lenses), some are not.  The brighter stars stand out better in the non-corrected images.

The 2024 solar eclipse seen from Santa Fe

The day started cloudy and mostly stayed cloudy, but the clouds were thin enough at times to get a view of the partial eclipse from Santa Fe.  An Orion 80mmED f/7.5 refractor was used for photography.  This telescope was riding on a Celestron CG-4 motor-driven equatorial mount.  The camera was an Olympus E-M5iii looking through a ND-0.6 filter and a Lunt solar wedge.  For visual observation we used a Celestron  80mm f/5 refractor equipped with a front-mounted Kendrick Al-mylar solar filter.  A black-polymer "window frame" filter was used for non-telescopic viewing.

A few minutes before maximum eclipse (12:30 MDT).

 The variable and at-times thick clouds disrupted the planned-interval exposures, so I pretty much clicked away at random in case the clouds got worse.

This false-color nine-image montage spans about 45 minutes:

The bottom-left image is near maximum eclipse.

This is a natural-color animation created from all the images:

There were occasional moments of relative clarity:

Sun spots.  ISO 200, 1/200 s.

ISO 200, 1/640 s.

This is a view through the black-polymer window-frame filter using a Nikon 85mm lens on a Sony A7iii camera:

Comet 12P/Pons-Brooks

 Comet 12P/Pons-Brooks is a short-period "Halley-type" comet that was discovered in 1812.  It has an orbital period of 71 years.  It is currently visible with binoculars low in the western sky during twilight. 

Catching the comet photographically from my back-yard location in urban Santa Fe is very challenging because of trees, walls, and electrical wires.  By the time twilight has faded enough to get good exposures the comet has been obscured by all the neighborhood clutter.  

Here is the way it looked at 8:30 pm tonight:

E-M5 + Rokinon 135mm f/2.  ISO 800, 20 s.

This is a stack of three 20-sec exposures, with some contrast enhancement:

E-M5 + Rokinon 135mm f/2.  ISO 800, (20 s × 3).  3° × 2° FOV.

A quick Google search reveals that it is being called the "Devil" comet, the "Horned" comet, the "Mother-of-Dragons" comet, the "Once-in-a-lifetime" comet, and probably some other eye-rolling names.   Visually, it's just a fairly ordinary comet.   There are, however, some very beautiful long-exposure photos showing up on the internet.

La Superba -- Y CVn

 Another star of interest in the constellation Canes Venatici is "La Superba", Y Canus Venaticorum or Y CVn.  It is one of the reddest stars in the sky.  It belongs to a class of stars called "Carbon Stars".  These stars have large amounts of carbon compounds in their atmosphere which absorb short wavelengths.  The name was coined by the 19th-century astronomer priest Angelo Secchi.

credit: SkySafariAstronomy.com

La Superba.  E-M5 + Rokinon 135mm f/2.  ISO 800, 30 s.  2° FOV.

E-M5iii + AT72mmEDII.  ISO 1600, 10 s.  0.5° FOV.

E-M1iii + Tokina AT-X 80-200mm f/2.8 @ 200mm + softon filter.  ISO 1600, 30 s.

This last image shows the red color best.  The lens is an old Nikon-mount manual-focus zoom adapted to the micro-four-thirds E-M1iii.  Sky brightness was sqml=19.62.